1. Field of the Invention
The present invention relates to an anti-theft device for vehicles. In particular, the present invention relates to an anti-theft device for vehicles provided with tyres and a method for activating the anti-theft device.
2. Description of the Related Art
It is known, according to the state of the art, that most anti-theft devices are installed inside the car and are based on varyingly improved techniques in which perimeter-defense sensors of various types are used, said sensors being often associated with a control system based on the recognition of coded keys necessary for activation/deactivation of the anti-theft device itself. These keys transmit, via radio, a cede to said control system, using suitably reserved frequency ranges.
For example, U.S. Pat. Nos. 6,194,997 and 4,805,723 describe anti-theft devices for motor vehicles in which a monitoring device inside the vehicle is able to detect the presence of persons inside the vehicle. This monitoring device is activated by a key which, at the same time, is able to lock the doors for access to the vehicle.
The Applicant has observed that, although very versatile and efficient and, in principle, capable of being incorporated into systems for monitoring the position of the vehicle of the GPS (Ground Position System) type, the traditional anti-theft devices are often affected by factors which reduce the degree of reliability thereof. Among these the following may be mentioned:
the control units have in fact a standardized location, thereby in principle resulting in the possibility of their being discovered and deactivated by criminals with a certain technical knowledge;
not all the anti-theft devices, in particular if low-cost, are able to detect any movement of the vehicle if it has been raised by a special mechanical means; this especially if the vehicle is actually raised from the ground and removed without causing rolling of the wheels;
traditional anti-theft devices, if removed, do not necessarily cause an irreversible deterioration or locking of certain vital components in the mechanical structure of the vehicle;
in any case, even in the most inexpensive versions; anti-theft systems often constitute a not negligible fraction of the cost of the vehicle; this discourages their use in many types of utility or low-power vehicles which, on the other hand, appear to be one of the preferred targets of car thieves.